Recently, with the development of mobile devices such as smartphones and tablet PCs, thinning and slimming of substrates for display are required. Glass or tempered glass is commonly used as a material having excellent mechanical properties on windows or front boards for displays of mobile devices. However, the glass causes the weight increase of the mobile devices due to its own weight, and has a problem of breakage due to an external impact.
Therefore, plastic resin is being studied as a substitute for glass. The plastic resin composition is lightweight but hardly has a risk of cracking and thus are suitable for the trend of pursuing lighter mobile devices. In particular, in order to achieve a composition having high hardness and abrasion resistance properties, a composition for coating a hard coating layer onto a support substrate has been proposed.
As a method of improving the surface hardness of the hard coating layer, a method of increasing the thickness of the hard coating layer can be considered. In order to ensure the surface hardness enough to replace the glass, it is necessary to implement a thickness of a certain hard coating layer. However, as the thickness of the hard coating layer is increased, the surface hardness may be increased but the occurrence of wrinkles and curls are increased due to curing shrinkage of the hard coating layer, and at the same time cracking and peeling of the coat layer are likely to occur. Therefore, the practical application of this method is not easy.
Meanwhile, a display in which a part of the display device is bent or flexibly warped for aesthetic and functional reasons has recently been attracting attention, and this tendency is particularly noticeable in mobile devices such as smartphones and tablet PCs. However, since glass is not suitable for use as a cover plate for protecting such a flexible display, it needs to be replaced with a plastic resin or the like. However, for that purpose, it is not easy to produce a thin film having sufficient flexibility while exhibiting a glass level of high hardness.